Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A pyroelectric infrared body sensing switch circuit comprises an
amplification circuit, a delay unit, an execution unit, and an infrared
detection circuit comprising one or more pyroelectric infrared detection
elements. A power unit comprises first and second power circuits. Each of
the first and second power circuits receives AC power and supplies DC
power through RC voltage reduction, full-wave rectification, filtration,
and voltage stabilization. The first power circuit supplies power to the
execution unit and the second power circuit supplies power to the
infrared detection circuit, the amplification circuit, and the delay
unit. A signal outputted from the infrared detection circuit is inputted
to the amplification circuit. A signal outputted from the amplification
circuit controls the activation of the delay unit. A signal output from
the delay unit controls the execution unit. The signal outputted from the
infrared detection circuit comprises superposed output signals from the
one or more pyroelectric infrared detection elements.

Claims:

1. A pyroelectric infrared body sensing switch circuit, comprising: a
power unit comprising a first power circuit and a second power circuit,
each power circuit comprising: a voltage reducer; a rectifier; a filter;
and a voltage stabilizer; an infrared detection circuit comprising one or
more pyroelectric infrared detection elements; an amplification circuit;
a delay unit; and an execution unit, wherein: each of the first power
circuit and the second power circuit receives AC power from an AC power
supply and supplies DC power through RC voltage reduction by the voltage
reducer, full-wave rectification by the rectifier, filtration by the
filter, and voltage stabilization by the voltage stabilizer, the first
power circuit supplies power to the execution unit and the second power
circuit supplies power to the infrared detection circuit, the
amplification circuit, and the delay unit, a first signal outputted from
the infrared detection circuit is inputted to the amplification circuit,
a second signal outputted from the amplification circuit controls the
activation of the delay unit, a third signal output from the delay unit
controls the execution unit, the first signal outputted from the infrared
detection circuit comprises superposed output signals from the one or
more pyroelectric infrared detection elements.

2. The circuit of claim 1, wherein an infrared detection and signal
amplification unit comprises the infrared detection circuit and the
amplification circuit.

3. The circuit of claim 1, wherein the one or more pyroelectric infrared
detection elements are grouped, and the infrared detection circuit
comprises one or more groups of pyroelectric infrared detection elements.

4. The circuit of claim 1, wherein the delay unit comprises a monostable
circuit equipped with an RC charge subcircuit to control the delay time,
and the RC charge subcircuit comprises: a charge capacitor; and an
amplification triode comprising a collector and a base, wherein the
charge capacitor of the RC charge subcircuit is connected in parallel
across the collector and the base to form a charge bypass of the charge
capacitor.

5. The circuit of claim 4, further comprising: a single-key bistable unit
comprising a wire-and connection to the delay unit, wherein the working
power of the single-key bistable unit is controlled by the output of the
delay unit, and wherein the output of the single-key bistable unit and
the output of the delay unit control the execution unit jointly through
the wire-and.

6. The circuit of claim 1, further comprising: a single-key bistable unit
comprising a wire-and connection to the delay unit, wherein the working
power of the single-key bistable unit is controlled by the output of the
delay unit, and wherein the output of the single-key bistable unit and
the output of the delay unit control the execution unit jointly through
the wire-and.

7. The circuit of claim 4, further comprising: a plurality of
amplification resistors; a discharge diode; a comparator circuit
comprising an output; and a trigger subcircuit comprising: a trigger
current limiting resistor; a trigger NPN switch triode comprising a base,
an emitter, and a collector, the emitter of the trigger NPN switch triode
connected to the negative pole of the power supply through the trigger
current limiting resistor, the base of the trigger NPN switch triode
connected to the output of the comparator circuit; a trigger capacitor
comprising a positive pole connected to the collector of the trigger NPN
switch triode; and first and second trigger resistors connected in series
with the trigger capacitor and connected across the positive and negative
poles of the power supply, the trigger NPN switch triode, and the trigger
current limiting resistor, wherein: the second power circuit further
comprises a positive pole and a negative pole, the delay unit further
comprises: a delay unit time base circuit comprising a trigger end, a
discharge end, and a threshold end; and a delay unit monostable circuit
comprising external components and a delay unit amplification triode, the
delay unit amplification triode comprising a base, a collector, and an
emitter, the collector and emitter of the delay unit amplification triode
are connected across the discharge end and threshold end of the delay
unit time base circuit and the negative pole of the second power circuit,
respectively, the collector of the delay unit amplification triode is
connected to the positive pole of the second power circuit through the
plurality amplification resistors, at least one of the plurality of
amplification resistors also acts as a resistor in the RC charge
subcircuit, the charge capacitor is connected in parallel across the
collector and base of the delay unit amplification triode, the discharge
diode is connected in parallel across the base and the emitter of the
delay unit amplification triode, the trigger subcircuit connects the
amplification circuit and the delay unit, and the first and second
trigger resistors are connected at a connection point, and the connection
point is connected with the trigger end of the delay unit time base
circuit such that an output signal from the amplification unit controls
the operation of the delay unit.

8. The circuit of claim 5, further comprising: a plurality of
amplification resistors; a discharge diode; a comparator circuit
comprising an output; and a trigger subcircuit comprising: a trigger
current limiting resistor; a trigger NPN switch triode comprising a base,
an emitter, and a collector, the emitter of the trigger NPN switch triode
connected to the negative pole of the power supply through the trigger
current limiting resistor, the base of the trigger NPN switch triode
connected to the output of the comparator circuit; a trigger capacitor
comprising a positive pole connected to the collector of the trigger NPN
switch triode; and first and second trigger resistors connected in series
with the trigger capacitor and connected across the positive and negative
poles of the power supply, the trigger NPN switch triode, and the trigger
current limiting resistor, wherein: the second power circuit further
comprises a positive pole and a negative pole, the delay unit further
comprises: a delay unit time base circuit comprising a trigger end, a
discharge end, and a threshold end; and a delay unit monostable circuit
comprising external components and a delay unit amplification triode, the
delay unit amplification triode comprising a base, a collector, and an
emitter, the collector and emitter of the delay unit amplification triode
are connected across the discharge end and threshold end of the delay
unit time base circuit and the negative pole of the second power circuit,
respectively, the collector of the delay unit amplification triode is
connected to the positive pole of the second power circuit through the
plurality amplification resistors, at least one of the plurality of
amplification resistors also acts as a resistor in the RC charge
subcircuit, the charge capacitor is connected in parallel across the
collector and base of the delay unit amplification triode, the discharge
diode is connected in parallel across the base and the emitter of the
delay unit amplification triode, the trigger subcircuit connects the
amplification circuit and the delay unit, and the first and second
trigger resistors are connected at a connection point, and the connection
point is connected with the trigger end of the delay unit time base
circuit such that an output signal from the amplification unit controls
the operation of the delay unit.

9. The circuit of claim 7, further comprising a delay unit capacitor
connected between the trigger end of the delay unit time base circuit and
the base of the trigger NPN switch triode.

10. The circuit of claim 8, further comprising a delay unit capacitor
connected between the trigger end of the delay unit time base circuit and
the base of the trigger NPN switch triode.

11. The circuit of claim 5, wherein: the second power circuit further
comprises a positive pole and a negative pole, the single-key bistable
unit further comprises: a single-key time base circuit comprising an
output end, a discharge end, a trigger end, and a control end; first,
second, and third single-key resistors; first and second single-key
capacitors; and a button, the first single-key resistor and the second
single-key resistor are connected in series and are connected across the
positive and negative poles of the second power circuit, the third
single-key resistor and second single-key capacitor are connected between
the output end of the single-key time base circuit and the negative pole
of the second power circuit, the first and second single-key resistors
are connected at a single-key connection point, and the trigger end and
the control end of the single-key time base circuit are connected
together and then connected to the single-key connection point, the
button is provided between the connection point between the third
single-key resistor and the second single-key capacitor and the
connection point of the trigger and control pins of the single-key time
base circuit, and the discharge end of the single-key time base circuit
connects to the output of the delay unit, and the single-key time base
circuit controls the delay unit and the execution unit.

12. The circuit of claim 6, wherein: the second power circuit further
comprises a positive pole and a negative pole the single-key bistable
unit further comprises: a single-key time base circuit comprising an
output end, a discharge end, a trigger end, and a control end; first,
second, and third single-key resistors; first and second single-key
capacitors; and a button, the first single-key resistor and the second
single-key resistor are connected in series and are connected across the
positive and negative poles of the second power circuit, the third
single-key resistor and second single-key capacitor are connected between
the output end of the single-key time base circuit and the negative pole
of the second power circuit, the first and second single-key resistors
are connected at a single-key connection point, and the trigger end and
the control end of the single-key time base circuit are connected
together and then connected to the single-key connection point, the
button is provided between the connection point between the third
single-key resistor and the second single-key capacitor and the
connection point of the trigger and control pins of the single-key time
base circuit, and the discharge end of the single-key time base circuit
connects to the output of the delay unit, and the single-key time base
circuit controls the delay unit and the execution unit.

Description:

[0001] This application claims the benefit of priority of Chinese patent
application 201020170544.X, filed Apr. 22, 2010, the content of which is
incorporated herein by reference in its entirety.

[0003] Being capable of receiving weak far-infrared rays emitted from
bodies for the purpose of detecting the existence of bodies in a certain
area, pyroelectric infrared body sensing switch circuits are widely used
in body detection applications such as burglar alarms, equipment
safeguard devices, lighting controls in public places of dwelling houses,
etc. Pyroelectric infrared body sensing switches are especially useful
for lighting in public places of dwelling houses, where the switch can
turn on automatically when a person passes by and keep a light on for a
certain delay time, and then turn the light out after the person leaves.
In this way, the switch can save much energy. The switch conforms to the
environmental protection concept and is convenient for use.

[0004] Therefore, pyroelectric infrared body sensing switches are used for
lighting control in more and more public places of dwelling houses. The
present pyroelectric infrared body sensing switch circuit normally
consists of a power supply unit, infrared detection & signal
amplification unit, delay unit and execution unit. After an infrared
signal from a human body is detected by the infrared detection device and
is amplified by the signal amplification unit, it triggers the delay unit
to start the time delay. After the preset time lapses, it outputs a
signal to the execution unit to turn off the light or to control other
appliances to act accordingly. Normally the delay unit adopts the time
constant of the RC charge circuit, which is composed of a charge
capacitor and a charge resistor as the reference. As restricted by the
capacitance and volume of the capacitor, this mode can not provide a long
time delay. Meanwhile, when the capacitance of the capacitor is more than
200 μF, the timing accuracy deteriorates, causing certain restrictions
to the application occasions of the present pyroelectric infrared body
sensing switch.

[0005] In addition, the power supply unit of the present pyroelectric
infrared body sensing switch normally adopts a single power supply to
provide the whole switch with power. There are two commonly used circuit
forms. One is an RC voltage reduction mode, which has the advantages of
low cost and small volume but also has the disadvantage of a relatively
low power of the power supply. The other mode is a transformer voltage
reduction mode. Although this mode can work more reliably and can provide
a higher power, the volume of the power supply is large and the cost is
high.

SUMMARY

[0006] The present pyroelectric motion detection circuit overcomes the
deficiency of the present technology and provides a circuit which has a
wide voltage range, a low power consumption, an extensive detection
angle, a high accuracy, a long time delay, and a low cost.

[0007] In one embodiment a pyroelectric infrared body sensing switch
circuit, comprises an amplification circuit, a delay unit, an execution
unit, a power unit, and an infrared detection circuit. The power unit
comprises a first power circuit and a second power circuit, each power
circuit comprising a voltage reducer, a rectifier, a filter, and a
voltage stabilizer. The infrared detection circuit comprises one or more
pyroelectric infrared detection elements.

[0008] Each of the first power circuit and the second power circuit
receives AC power from an AC power supply and supplies DC power through
RC voltage reduction by the voltage reducer, full-wave rectification by
the rectifier, filtration by the filter, and voltage stabilization by the
voltage stabilizer. The first power circuit supplies power to the
execution unit and the second power circuit supplies power to the
infrared detection circuit, the amplification circuit, and the delay
unit.

[0009] A signal outputted from the infrared detection circuit is inputted
to the amplification circuit. A signal outputted from the amplification
circuit controls the activation of the delay unit. A signal output from
the delay unit controls the execution unit. The signal outputted from the
infrared detection circuit comprises superposed output signals from the
one or more pyroelectric infrared detection elements.

[0010] It is to be understood that both the foregoing general description
and the following detailed description are exemplary and explanatory only
and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute
a part of this specification, illustrate several embodiments of the
invention and together with the description, serve to explain the
principles of the invention.

[0012] FIG. 1 is an example of an electrical block diagram.

[0013] FIG. 2A is an example of an electrical schematic of a pyroelectric
motion detection circuit.

[0014]FIG. 2B is a continuation of the example of the electrical
schematic of a pyroelectric motion detection circuit.

DETAILED DESCRIPTION

[0015] Reference will now be made in detail to the present exemplary
embodiments, examples of which are illustrated in the accompanying
drawings. Wherever possible, the same reference numbers will be used
throughout the drawings to refer to the same or like parts.

[0017] As shown in FIGS. 2A and 2B, which connect points A-A, B-B, and
C-C, the power unit consists of two groups of power circuits. One group
of DC power supply provides the execution unit with working power, in
which the DC power supply is obtained from an AC power supply through RC
voltage reduction of the resistor R29 and the capacitor C14, full-wave
rectification of the diodes D5-D8, filtration of the capacitor C15 and
voltage stabilization of the voltage stabilization diode D15. The other
group provides the remaining part of the pyroelectric infrared body
sensing switch circuit with working power, in which the DC power supply
is obtained from AC power supply through RC voltage reduction of the
resistor R28 and the capacitor C13, full-wave rectification of the diodes
D1-D4, filtration of the capacitor C12 and voltage stabilization of the
voltage stabilization diode D14 and 3-end voltage stabilizer.

[0018] To obtain a relatively large detection angle, the infrared
detection & signal amplification unit can be provided with one or more
groups of pyroelectric infrared detection elements. The output signals of
all the pyroelectric infrared detection elements are superposed and then
inputted to the amplification unit. Normally, depending on the actual
conditions, 2-4 groups of pyroelectric infrared detection elements are
sufficient. In this example, two groups of pyroelectric infrared
detection elements are provided. The output ends (S ends) of the two
groups of pyroelectric infrared detection elements are connected together
through the resistor R4 and the resistor R5, allowing the output signals
of the pyroelectric infrared detection elements to be superposed and then
inputted into the amplification unit. The signal amplification unit shall
be able to amplify the signals detected by the pyroelectric infrared
detection elements. Moreover, it is preferable that the output should
control the delayed startup of the delay unit after a certain signal
intensity is obtained in order to improve the anti-interference ability.

[0019] In this example, two operational amplifiers A1 and A2 and their
external elements are used to form the amplification circuit and
comparator circuit respectively. The output end of the amplification
circuit is connected to the reverse-phase input end of the comparator,
and the normal-phase input end of the comparator is connected with a
reference voltage. The reference voltage is obtained from the voltage
shunting subcircuit composed of the resistor R10, the resistor R12, and
the variable resistor W1.

[0020] In this pyroelectric infrared body sensing switch circuit, the
delay unit can be composed of various monostable circuits equipped with a
RC charge subcircuit to control the delay time. The charge capacitor of
the said RC discharge subcircuit is connected in parallel across the
collector and base of an amplification triode so that the amplification
triode may form the charge bypass of the charge capacitor. The output
signal of the said infrared detection & signal amplification unit
controls the working of the delay unit.

[0021] In this embodiment, the delay unit is composed of a 555 time base
circuit IC2 and its monostable circuit which consists of external
components including amplification triode Q2. NPN type triode is selected
for the amplification triode Q2. The collector and emitter of the
amplification triode Q2 are connected across the discharge end and
threshold end of the 555 time base circuit and the negative pole of the
power supply respectively. The collector of the triode Q2 is connected to
the positive pole of the power supply through the load resistor R14 and
the resistor W2, which also act as a charge passage. The charge capacitor
C8 is connected in parallel across the collector and base of the
amplification triode Q2. Discharge diode D9 is connected in parallel
across the base and emitter. The amplification triode Q2 forms the charge
bypass of the charge capacitor C8.

[0022] The circuit is also provided with a trigger subcircuit that
connects the amplification circuit and the delay unit. The trigger
subcircuit includes the resistor R15, resistor R13, and capacitor C7
connected in series across the positive and negative poles of the power
supply, the NPN switch triode Q3, and the current-limiting resistor R16.
The emitter of the switch triode Q3 is connected with the negative pole
of the power supply through the current-limiting resistor R16. The
collector of the switch triode Q3 is connected with the positive pole of
the capacitor C7. The output of the comparator circuit is connected with
the base of the switch triode Q3.

[0023] The connection point of resistor R15 and resistor R13 is connected
with the trigger end of the 555 time base circuit IC2. In this way, the
output signal of the infrared detection & signal amplification unit can
control the operation of the delay unit.

[0024] To avoid the occasion that the lighting goes out before a person
leaves the detection scope of the pyroelectric infrared detection
elements because the person stays in the scope for a period longer than
the set delay time, in this circuit, a capacitor C9 is connected between
the trigger end of the 555 time base circuit IC2 and the base of the
switch triode Q3. The output end of the 555 time base circuit IC2 is
connected with the composite amplification circuit composed of the
amplification triode Q4 and amplification triode Q5 to control the
photocoupler OC, and further to control the action of the working power
of the relay J by controlling the on-off of the switch triode Q6. In this
way, control to the lighting (or other electrical appliances) is
realized.

[0025] The operational principle of this pyroelectric infrared body
sensing switch circuit is as follows: When neither of the two groups of
pyroelectric infrared detection elements detects any infrared signal from
a human body, the normal-phase input end of the amplifier A1 is at a high
level and the output is at a high level. This means that the
reverse-phase input end of the amplifier A2 is at a low level and the
output is at a low level. The switch triode Q3 is cut off. Therefore, the
second pin, i.e. trigger end, of the 555 time base circuit IC2 is at a
high level and the output is at a low level. The composite amplification
circuit composed of the amplification triode Q4 and amplification triode
Q5 is cut off. No current passes through the photocoupler. The switch
triode Q6 is cut off. The relay J has no working power. The external
lighting (or other electrical appliance) is off (or does not work). In
the meantime, the charge capacitor C8 discharges through the seventh pin
of the 555 time base circuit IC2, the internal triode, and the discharge
diode D9.

[0026] When either of the two groups of pyroelectric infrared detection
elements detects any infrared signal from a human body, the normal-phase
input end of the amplifier A1 is at a low level and the output is at a
low level. This means that the reverse-phase input end of the amplifier
A2 is at a low level and the output is at a high level. The switch triode
Q3 is broken over. Therefore, the second pin, i.e. trigger end, of the
555 time base circuit IC2 is at a low level and the output is at a high
level. The composite amplification circuit composed of the amplification
triode Q4 and amplification triode Q5 is broken over. Current passes
through the photocoupler. The switch triode Q6 is broken over. The relay
J actuates under the action of electricity. The external lighting (or
other electrical appliance) turns on (or works).

[0027] In the meantime when the second pin, i.e. the trigger end, of the
555 time base circuit IC2 is at a low level and the output is at a high
level, the internal triode of the 555 time base circuit IC2 is cut off.
The current of the power supply flows through the resistor R14, the
variable resistor W2, and the emitter of the amplification triode Q2 to
charge the charge capacitor C8 until the voltage at the sixth pin, i.e.
the threshold end, of the 555 time base circuit IC2 is higher than 2/3
VCC when the output end of the 555 time base circuit IC2 is converted to
low level. The external lighting (or other electrical appliance) is off
(or does not work), and the time is charge time.

[0028] Because the amplification triode Q2 forms the charge bypass of the
charge capacitor C8, the charge current of the charge capacitor C8 is
only one part in hFE (amplification factor of the triode Q2) of the
collector current of the triode Q2. Therefore, for the same charge
current, most of it is shunted by the collector of the triode Q2. So the
voltage increasing rate of the delay capacitor C8 is only one part in hFE
of the original amplification triode Q2, and the monostable delay time is
hFE times the original 1.1 RC, i.e. 1.1hFE RC seconds. In this way, a
long delay is obtained with a capacitor of small capacitance without
sacrificing the delay precision.

[0029] In some occasions, the switch needs to be controlled manually. To
realize this function concurrently, a single-key bistable unit is added
to the above described scheme. The working power of the single-key
bistable unit is controlled by the output of the delay unit. The output
of the single-key bistable unit and the output of the delay unit control
the execution unit jointly through the wire-and.

[0030] In this embodiment, the single-key bistable unit is composed of the
555 time base circuit IC3 and the external elements including resistor
R24, resistor R25, resistor R26, capacitor C16 and capacitor C17. The
resistor R24 and resistor R25, after being connected in series, are
connected across the positive and negative poles of the power supply. The
resistor R26 and capacitor C17 are connected between the output end of
555 time base circuit IC3 and the negative pole of the power supply. The
second and fifth pins of 555 time base circuit IC3, i.e. the trigger end
and the control end, are connected together and then connected to the
connection point of the resistor R24 and resistor R25.

[0031] Between the connection point of the resistor R26 and capacitor C17
and the interconnection point of the second and fifth pins of the 555
time base circuit IC3, a button AN is provided, which forms the
single-key bistable unit. Once the button AN is pressed, the level of the
output end of the single-key bistable unit, i.e. the seventh pin of the
555 time base circuit IC3 changes. The seventh pin of the 555 time base
circuit IC3, i.e. the discharge end, is connected with the output control
circuit of the delay unit for the purpose of controlling the execution
unit jointly. In this embodiment, it is connected to the connection point
of the resistor R22 and the resistor R23 to form the "wire-and" relation.
That is to say, when either the output of the delay unit or the seventh
pin of the 555 time base circuit IC3 is at a low level, no current will
flow through the photocoupler. The switch triode Q6 is cut off, the relay
J has no working power, and the external lighting (or other electrical
appliance) is off (or does not work).

[0032] However, the eighth pin, i.e. the power supply end, of the 555 time
base circuit IC3 is connected to the collector end of the amplification
triode Q5 in the output control circuit of the delay unit, making the
working power of the single-key bistable unit be controlled by the output
of the delay unit to ensure that the button AN functions only when any of
the pyroelectric infrared detection elements detects an infrared signal
from a human body.

[0033] Since the single-key button can be used as a normal switch in this
setting, it can control the working of the execution unit at the same
time when the infrared detection device detects the infrared signal from
human body, improving the function of the switch circuit. It is
preferable that the single-key bistable unit and the delay unit be
composed of the 555 time base circuit and its external elements. In this
case, the structure of the circuit can be simpler and the work can be
stable.

[0034] As compared with the prior art, since multiple pyroelectric
infrared detection elements are set in this pyroelectric motion detection
circuit, the several pyroelectric infrared detection elements can face to
different directions, increasing the detection angle. In addition, as a
dedicated circuit for DC power supply is used to provide the execution
unit with working power, the circuit structure can be simpler. This
utility model also has a feature that the charge capacitor is connected
in parallel across the collector and base of the amplification triode.
The amplification triode forms the charge bypass of the charge capacitor.
The charge current of the charge capacitor is only one part in hFE of the
triode collector current. Therefore, for the same charge current, most of
it is shunted by the collector of the triode. So the voltage increasing
rate of the delay capacitor is only one part in hFE of the original
device without the amplification triode and the monostable delay time is
hFE times the original 1.1 RC, i.e. 1.1hFE RC seconds. In this way, a
long delay is obtained with a capacitor of small capacitance without
sacrificing the delay precision.

[0035] In the preceding specification, various preferred embodiments have
been described with reference to the accompanying drawings. It will,
however, be evident that various other modifications and changes may be
made thereto, and additional embodiments may be implemented, without
departing from the broader scope of the invention as set forth in the
claims that follow. The specification and drawings are accordingly to be
regarded in an illustrative rather than restrictive sense.

[0036] Other embodiments of the invention will be apparent to those
skilled in the art from consideration of the specification and practice
of the invention disclosed herein. It is intended that the specification
and examples be considered as exemplary only, with the true scope and
spirit of the invention being indicated by the following claims.